Serial C:Inside The Spaceship(aka The Edge Of Destruction,
Beyond The Sun)

Plot

Something is very wrong with the TARDIS. The doors open to reveal a white
void, clock faces melt, and each of its occupants behave in an
increasingly erratic, paranoid and even violent manner. Has some strange
force invaded the TARDIS, or is one of the time travellers actually
sabotaging the Ship? As the seconds slip away and hysteria mounts, the
truth may doom them all.

Production

Doctor Who was nearly cancelled before it even began. In late
October 1963, BBC Chief of Programmes Donald Baverstock had effectively
indicated that he would not allow the show to proceed beyond its initial
four-part serial, due to perceived cost overruns. Head of Drama Sydney
Newman and Head of Serials Donald Wilson -- two of the chief architects of
Doctor Who -- intervened and managed to assuage Baverstock's
concerns. The result was that Baverstock agreed to authorise the
production of the first thirteen Doctor Who episodes.

Unfortunately, at this stage the first three serials were 100,000 BC (four parts), The Daleks
(seven parts) and John Lucarotti's Marco Polo
(also seven parts). Because the thirteen-episode order would only take the
series up to the second installment of Lucarotti's story, it was agreed
that a new two-part adventure should be developed which would be inserted
in between The Daleks and Marco Polo. Story editor David Whitaker agreed to
take on the task of writing these scripts over the course of a weekend. By
the end of October, Inside The Spaceship was officially announced
as Serial C. (Some references cite “Beyond The Sun” as an
alternative title for this story, but in fact this was a working title for
The Daleks. The confusion arose when a
mid-Seventies BBC Enterprises document used the incorrect title.)

The first three stories would exploit each of the settings
envisaged for Doctor Who: past, future and
“sideways”

Due to concerns about a story editor commissioning himself, Whitaker
agreed that he would be credited only as the adventure's author. He was
not formally commissioned until several months later, on February 10th,
1964. As the basis of his story, Whitaker turned to an idea he had mooted
during July 1963 of a TARDIS-based adventure which would serve as a
showcase for both the Ship and its passengers. Moreover, it would enable
the serial to be produced very cheaply, further allaying concerns about
Doctor Who's budget. As an added bonus, this would allow the first
three serials to exploit the three different types of settings originally
envisaged for the programme -- past, future and “sideways” --
something which had been lost when CE Webber's “The Giants”
(in which the Doctor and his companions are shrunk to just inches in
height) had been dropped as the debut adventure.

The director originally assigned to Inside The Spaceship was Paddy
Russell, one of the first female directors at the BBC. Russell was not
available for the studio dates, however, and Doctor Who's associate
producer, Mervyn Pinfield, was suggested as her replacement. Ultimately,
Richard Martin -- who had directed some episodes of the preceding story,
The Daleks -- was pencilled in to helm Serial
C. As recording approached, slight changes were made to the adventure's
climax, having Barbara alone deducing that the TARDIS was trying to
communicate with its passengers (whereas originally this achievement was
shared with Ian). In rehearsals, the resolution to this crisis was made
more exciting: Whitaker's script had simply described the Doctor flipping
the Fast Return Switch to save the Ship.

Subsequently, it was realised that Martin would not be available to helm
The Brink Of Disaster. As such, it was decided to allocate the
episode to Frank Cox, who had recently completed the directors' training
course. Cox had originally aspired to be an actor but, after being refused
admission to RADA, became a floor assistant at the BBC.

Requiring no filming, nor indeed any supporting cast, Inside The
Spaceship went before the cameras on two consecutive Fridays starting
on January 17th, at Lime Grove Studio D.